Functional Decomposition Example

Let's take the example of cleaning a house. At the top level, one way of breaking down the problem would be something like this:

Clean the bathrooms

Clean the bedrooms

Clean the living room

Clean the dining room

Clean the kitchen

Note that all of the steps are at about the same level (clean a room or multiple rooms of the same type), and none of those steps gets more involved than any other steps.

At the next level, each of those types of rooms would be broken down into the steps necessary to do each. So, cleaning a bathroom could decompose into:

Clean the tub

Clean the toilet

Clean the mirrors

Clean the counters

Clean the floor

At this level, you've probably noticed that the detailed steps are still missing. And yet, the instructions are at the same level of detail (a part of a room at this level instead of an entire room). Each of the types of rooms listed in the first level would have their own list of parts to clean.

It's at the third level of breakdown (in this particular example) where the specifics to each type of thing gets broken down.

Now, if the details the first round of steps were already known to the person doing the cleaning, that level of instruction is deep enough. You would specify in the "What you need to know" section what the required training would include.

Another thing of note: if you were giving these instructions to a person who was going to clean your house, and you make comments about why something happens the way it does or when in the sequence it does, those are the types of things that get listed in the "What you need to know" section.